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CVE-2026-45108

Himmelblau: Authentication Bypass via Cross-User Local Session Impersonation in Device Authorization Grant (DAG) Flow

Published: May 27, 2026Updated: May 27, 2026 Sources: CVE List
NVD MITRE
8.4CVSS
HIGH

Himmelblau is an interoperability suite for Microsoft Azure Entra ID and Intune. From 2.0.0 to before 3.1.5 and 2.3.11, Himmelblau contained an authentication bypass vulnerability in the Device Authorization Grant (DAG) flow that allowed a user within the same Entra ID domain to obtain a local Unix session as another user by providing their own valid credentials. The vulnerability existed in the token_validate function, which validated domain aliases for legitimate multi-domain scenarios but failed to verify that the local part (username) of the authenticated user's UPN matched the requested account username. The function only compared domains, not the complete usernames. This vulnerability is fixed in 3.1.5 and 2.3.11.

EPSS Score
N/A
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available

CVSS Vector Breakdown

AV:NAC:HPR:LUI:NS:CC:HI:HA:L
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:LAvailability
Low

Weaknesses

CWE-863CWE-863: Incorrect Authorization

Affected Products

himmelblau
himmelblau-idm

Attack Graph

Products CVE Techniques Tactics

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Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

MITRE ATT&CK

2 techniques
Initial Access
View detailed technique mapping

References

https://github.com/himmelblau-idm/himmelblau/security/advisories/GHSA-pmxh-j4r6-88mv
github.com

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